std: - STDIN, STDOUT of the processexec:PROGRAM - fork() off a process and use its STDIN and STDOUTtty:TTYDEVICE - Open a TTY device (like a serial port) as clientpty:[PTYNAME] - Allocate a pseudo TTY device as mastertcp-client:HOSTNAME:PORT - Connect to another or the local host via TCP/IPtcp-server:[IPADDRESS:]PORT - Listen on a local port and wait for an incoming connectionunix-client:SOCKNAME - Connect to a local Unix domain socketunix-server:SOCKNAME - Listen on a local Unix domain socket